There are strong demands for heat insulation property and reduction of weight in the fields of interior parts of automobiles or the like such as various types of trims including door trims and side trims and various types of pillars, instrument panels as well as parts of household electrical appliances and building materials. As an approach for achieving such demands, JP-A-11-179752, for example, discloses automotive interior parts comprising olefin resin foam moldings comprising a skin layer and a foam layer.
Such a foam molding has a structure where a foam substrate comprising a foam layer having thereon a minute skin layer containing no voids is formed in one piece together with a projection such as a rib, a boss and a bracket through which the foam substrate is attached to a vehicle body or another member.
However, when a projection such as a rib, a boss and a bracket is attached to a foam substrate, a skin layer of the foam substrate and a circumferential face of the projection along the height direction of the projection defines a corner having a right angle or corresponding to the attaching angle at a joint between the projection and the foam substrate, so that there is a problem that when external force is applied, stress is concentrated to the corner and, therefore, the projection is easily broken. Hence, the present inventor studied to develop a thermoplastic resin foam molding comprising a substrate having a foam layer and a projection formed in one piece together with the substrate wherein the projection hardly separates from the substrate and is firmly jointed to the substrate. As a result, the present inventor has reached the present invention.